Screw extractor



g 1966 R. H CARLSON 3,263,533

said 10bular shank ortion, a maximum width less References cited by the Examine than the width of Said c lindrica1 Shank ortion Such hat the intersection of said lobular and c lindrica1 UNITED SATEs PATENTS Shank ortions dennes a shoulder for abuttin the l)863'046 6/ 1931 Glthens et 8l7l x ex osed end of a member to be extracted so as to 5 2,269,476 l/194l Poupitch 1Sll4 facilitate unthreading 0f said member to be ex 2,684,606 7/ 194 Brawley 8l-S3 tracted from its arent bod Z,694,328 11/ 1954 La Freniere 81S3 X the root surface ortions of the thread conv0lutions 3,19S,1S6 7/196S Phi ard 1010 nearest Said cylindrical unthreaded shank ortion 3,Z09 383 10/196S Carlson 10-1SZ bein in transverse cross section throu h said lo threaded shank ortion of reater width than the WILLIAM FELDMAN' Exn'mer' root surface ortions throu hout the femainin len th of said threaded shank ortion. G. WEIDENFELD, /1$S...m# Exm...#8*. 

1. A DEVICE FOR EXTRACTING BROKEN SCREW-THREADED MEMBERS FROM MATERIALS INTO WHICH SAID MEMBERS HAVE BEEN AT LEAST PARTIALLY THREADED, SAID DEVICE COMPRISING: AN ELONGATE MEMBER INCLUDING A CYLINDRICAL UNTHREADED SHANK PORTION HAVING A DRIVING MEANS AT ONE END AND A THREADED LOBULAR SHANK PORTION EXTENDING FROM THE OPPOSITE END THEREOF, SAID LOBULAR THREADED SHANK PORTION HAVING A SINGLE ROLLED SCREW THREAD WITH A PLURALITY OF CONVOLUTIONS EXTENDING CONTINUOUSLY FROM THE WORK-ENTERING END PORTION THEREOF TO A POSITION ADJACENT SAID OPPOSITE END OF SAID CYLINDRICAL SHANK PORTION, SAID THREAD, AS VIEWED AXIALLY, WINDING IN A RECEDING DIRECTION OPPOSITE TO THE RECEDING DIRECTION IN WHICH THE THREAD ON THE MEMBER TO BE EXTRACTED WINDS, SAID THREAD, AT LEAST IN SAID WORK-ENTERING END PORTION, HAVING A PITCH SURFACE WHICH IN CROSS SECTION IS IN THE SHAPE OF AN ARCUATE LOBULAR EQUILATERAL TRIANGLE HAVING CONVEXLY ARCUATE SIDES AND ARCUATE LOBES AT THE INTERSECTIONS OF SAID SIDES, THE CREST OF SAID THREAD IN SAID WORK-ENTERING END PORTION TAPERING INWARDLY IN A DIRECTION TOWARD THE TIP OF SAID END PORTION, THE LEAD ANGLE OF SAID THREAD BEING LESS THAN 30*, THE CREST SURFACE DEFINED BY SAID THREAD NEXT ADJACENT THE INTERSECTION OF SAID CYLINDRICAL AND LOBULAR SHANK PORTIONS HAVING, IN TRANSVERSE CROSS SECTION THROUGH SAID LOBULAR SHANK PORTION, A MAXIMUM WIDTH LESS THAN THE WIDTH OF SAID CYLINDRICAL SHANK PORTION SUCH THAT THE INTERSECTION OF SAID LOBULAR AND CYLINDRICAL SHANK PORTIONS DEFINES A SHOULDER FOR ABUTTING THE EXPOSED END OF A MEMBER TO BE EXTRACTED SO AS TO FACILITATE UNTHREADING OF SAID MEMBER TO BE EXTRACTED FROM ITS PARENT BODY. 